A symposium entitled "Bayesian Statistics in Science and Technology: Case Studies IV" will be held at Carnegie-Mellon University in Pittsburgh, Pennsylvania, on Friday, September 26 and Saturday, September 27, 1996. The symposium will include four extended presentations of applications of Bayesian research team. A contributed poster session will also be held. the objectives of the symposium are to: (I) Identify and focus attention on specific implementation and theoretical problems that hinder applications of Bayesian methods, and to identify candidate solutions; II) Provide a forum in which the interplay between statistical theory and practice will be explored in the context of concrete research projects; (III) Provide a small-meeting atmosphere within which junior investigators and graduate students can explore substantial Bayesian application with experienced researchers; and (IV) Produce a volume containing well-documented case studies and data sets suitable for use by researchers, practitioners, educators and students of applied statistics and other quantitative fields. As increasingly much background information becomes available to scientists undertaking an investigation, it is important to utilize previous knowledge effectively in designing studies and analyzing data. Bayesian statistical methods are tailored to this purpose. There have been many recent advances in Bayesian statistical theory and computation, but scientific meetings rarely spend substantial time discussing applications. The purpose of this symposium is to concentrate attention solely on applications of Bayesian statistics. the goal is to elucidate the interplay between theory and practice and thereby identify successful methods and indicate important directions for future research.